1. Field of the Invention
The present invention relates to a vehicle driving support apparatus that executes a follow-up cruise control or the like to follow a vehicle recognized in front of a subject vehicle.
2. Description of the Related Art
There have conventionally been various proposals for vehicle driving support apparatuses configured to recognize out-of-vehicle information in front of a vehicle by using onboard radar devices such as a millimeter wave radar and an infrared laser radar, imaging devices such as a stereo camera and a monocular camera, or a combination of the radar devices and the imaging devices, and execute various controls for the vehicle based on the recognized out-of-vehicle information. As an example of functions of such a driving support apparatus, a function of a follow-up cruise control to follow a vehicle in front when such a vehicle is detected (captured) in front of a subject vehicle is known widely.
The follow-up cruise control has been in practical use as part of an adaptive cruise control (ACC). In a typical use of the ACC, when the speed of the subject vehicle is in a high-speed range of a predetermined speed or higher (for example, a range of 40 km/h or higher), the follow-up cruise control is executed if a vehicle in front is detected, and a constant speed cruise control at a preset speed determined by the driver is executed if no vehicle in front is detected (or a vehicle in front is lost).
On the other hand, it has been a recent trend that the range to which the follow-up cruise control is applied is extended to a very low speed. Further, there have been proposed a technique of stopping the subject vehicle while maintaining a predetermined inter-vehicle distance from a vehicle in front when the vehicle in front has stopped (follow-up stop control) and a technique of starting the subject vehicle following a vehicle in front when the vehicle in front is detected to be started in a stop maintaining state after a follow-up stop.
In such a driving support apparatus, starting of the subject vehicle from a stopped state is typically permitted on the condition that the driver has made a predetermined operational input with a clear intention from the viewpoint of ensuring safety. For example, Japanese Unexamined Patent Application Publication (JP-A) No. 2005-247197 discloses a technique of permitting switching to a follow-up cruise control if the inter-vehicle distance between the subject vehicle and a vehicle in front is equal to or longer than a minimum target stopping distance and the vehicle in front has started during a preset amount of time (two seconds, for example) since a starting switch or a stopping switch was pressed by the driver in a stop maintaining state after a follow-up stop. In addition, JP-A No. 2005-247197 discloses a technique of advancing a vehicle by a predetermined distance (0.5 m, for example) if the inter-vehicle distance between the subject vehicle and a vehicle in front is equal to or longer than the minimum target stopping distance even if the vehicle in front is not started when the starting switch or the stopping switch was pressed by the driver.
However, the techniques disclosed in JP-A No. 2005-247197 as described above may cause the subject vehicle to be advanced at a timing that is not intended by the driver if a pedestrian or the like passes between the subject vehicle in a stop maintaining state and the vehicle in front, for example, because whether or not starting of the subject vehicle from a stopped state is to be permitted is determined basically based on the speed of the vehicle in front. Thus, if a pedestrian or the like passes between the subject vehicle in the stop maintaining state and a vehicle in front, for example, the distance from the subject vehicle to the pedestrian or the like may be temporarily recognized incorrectly as the inter-vehicle distance. In such case, the apparent inter-vehicle distance detected by the driving support apparatus changes in a manner that it becomes temporarily shorter and then immediately returns to the previous distance. When the apparent inter-vehicle distance suddenly changes in this manner, it may be recognized incorrectly that the vehicle in front has suddenly started, the subject vehicle may thus be started unintentionally even though the vehicle in front is in the stopped state, and then the follow-up stop control may begin immediately thereafter in the control process, which may give the driver an uncomfortable feeling.
Moreover, in such a driving support apparatus, the inter-vehicle distance between the subject vehicle and the vehicle in front that is detected by a radar device, an imaging device or the like may vary within a given error range due to various external factors or the like.
Therefore, according to the techniques disclosed in JP-A No. 2005-247197, if the starting switch or the stopping switch is pressed by the driver under the circumstances that the subject vehicle is maintained in the stopped state with an inter-vehicle distance to a vehicle in front slightly shorter than the minimum target stopping distance, the subject vehicle may be advanced at a timing that is not intended by the driver. Specifically, an inter-vehicle distance that is longer than the minimum target stopping distance may be temporarily detected due to detection errors of the inter-vehicle distance or the like at a point when a predetermined amount of time has passed since the starting switch or the stopping switch was pressed by the driver (at a point when approximately two seconds have passed since the switch was pressed, for example) under the circumstances that the subject vehicle is maintained in the stopped state with the inter-vehicle distance slightly shorter than the minimum target stopping distance. In such case, the subject vehicle may be started to advance even though the vehicle in front is in the stopped state, which may give the driver an uncomfortable feeling.